1. Field of the Invention
The present invention relates to a control device for a vehicle which comprises an automatic transmission, and in which an idling operation is stopped depending on predetermined stopping conditions, and in particular, the present invention relates to a control device incorporating a control technique which controls a motor-driven oil pump providing oil pressure for controllably operating the automatic transmission when the vehicle is in an idling stopped mode.
2. Description of the Related Art
An oil pressure control device, such as disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-99282, has been known in the art, which comprises a motor-driven oil pump in addition to a mechanical oil pump providing oil pressure for controllably operating a transmission or the like, and which controls the motor-driven oil pump so as to start the motor-driven oil pump upon receiving an engine stopping command and to stop the motor-driven oil pump upon receiving an engine restarting command.
In such oil pressure control devices, the motor-driven oil pump is constructed so as to be driven by being supplied electrical power from a battery device when the engine for driving the mechanical oil pump is stopped, and so as to provide oil pressure for controllably operating the transmission when, for example, the vehicle is going to start.
In such conventional oil pressure control devices, the motor-driven oil pump may not be operated or stopped at an appropriate timing if the motor-driven oil pump is controlled so as to be operated or stopped only by the engine stopping command or engine restarting command.
For example, if operation oil is evacuated from oil lines when the motor-driven oil pump is started after the engine and mechanical oil pump are stopped, it is necessary to set oil pressure to be at a predetermined standby pressure after filling the oil lines with the operation oil first in order to improve the responsiveness of the transmission at starting of the vehicle. To complete such operations in a short period, high capacity and high electrical power consumption of the motor-driven oil pump are required. As a result, problems are encountered in that efficiency of the motor-driven oil pump is lowered due increase in heat generation, or installability of the motor-driven oil pump in the vehicle is degraded due to increased size thereof.
On the other hand, if the motor-driven oil pump is started when, for example, oil pressure in the oil lines is relatively high upon receiving an engine stopping command, a problem is encountered in that efficiency of the motor-driven oil pump is lowered due to excessively increased oil pressure and electrical power consumption.
Moreover, if the motor-driven oil pump is stopped when, for example, discharging pressure of the mechanical pump is relatively low upon receiving an engine restarting command, oil pressure may be decreased, and responsiveness of vehicle at starting may be degraded. In contrast, if the motor-driven oil pump is stopped too late, a problem is encountered in that efficiency of the motor-driven oil pump is lowered due to excessively increased oil pressure and electrical power consumption.